Process for preparing modified styrene inteppolymers



Patented Oct. 24, 1950 PROCESS FOR PREPARING MODIFIED STYRENEINTEBPOLYMEBS Anthony H. Gleason, Per K. Frolich, and William J. Sparks,Westfield, N. J., assignors, by mesne assignments, to J asco,Incorporated, a corporation of Delaware No Drawing. Application December29, 1945,

Serial No. 638,515 7 6 Claims.

of technically valuable properties by the interpolymerization ofconjugated diolefin hydrocarbons containing from 4 to 6 carbon atoms permolecule with vinyl aromatic hydrocarbon compounds in emulsion withwater, emulsifying agent,

polymerization modifier, and catalyst while main-' taining the emulsionat a temperature of about 25 C; to 75 C.

This application is a continuation-in-part of application Serial No.408,814, filed August 29, 1941, and subsequently abandoned.

Polystyrene has outstandingly valuable electrical properties, but itsuse is limited because of its brittleness and general lack ofplasticity. Attempts to overcome this defect by the use of a plasticizerhave not been successful, because no plasticizing agent has been foundwhich does not materially detract from the desirable electricalproperties of pure polystyrene or does not adversely affect physicalproperties. Polyisobutylene of high molecular weight has repeatedly beensuggested for this purpose, since it is one of the few known materialsthatpossesses the same desirable electrical properties as polystyrene;This combination is not effective, however, since polystyrene is notcompatible with polyisobutylene at room temperature, and for thisparticular reason, these mixtures have not been physically suitable formost uses in the field of electrical insulation.

In the preparation of insulating compositions for high frequency radiotransmitting and receiving systems, (which systems require insulationshowing very low dielectric losses) many insulative compositions haveheretofore been proposed but none has been found which has the very lowhysteresis losses necessary to permit its use at ultra high frequencieswith a minimum of energy loss, and maximum transfer of energy throughthe insulated circuits; and a minimum of heat deterioration in theinsulation itself. Very low dielectric losses are most essential in highfrequency radio systems because the percentage energy loss of radiofrequency energy with a given dielectric material increases as thefrequency increases and at frequencies ranging from 1 megacycle up,especially at frequencies above 10 megacycles, the losses of energy fromdielectric hysteresis in ordinary dielectrics is prohibitively high.

Heretofore, interoplymers of vinyl aromatic hydrocarbons such as styrenewith diolefinic hydrocarbons have been prepared by the emulsionpolymerization reaction in the form of plastic, rubberlike masses havingsoft, rubber-like properties. The proportion of a diolefinic hydrocarbonand styrene in the finished plastic, rubber-like polymerizate asheretofore prepared was less than by weight of styrene. Furthermore, theconcentration of styrene in mixtures utilized in the prior art emulsionpolymerization reaction varied from about 20% up to about by weight whencopolymerized with a diolefinic hydrocarbon. The interpolymers obtainedby the emulsion polymerization reaction with these proportions ofstyrene are plastic rubber-like masses having soft, rubber-likeproperties, and are hydrocarbon compatible. They do not, however,possess the properties of hardness, toughness and extrudability whenblended with polybutenes or other hydro- I carbon polymers which arenecessary for the preparation of compositions for use as insulators forelectrical conductors.

With the above requirements in mind, it has been discovered that when avinyl aromatic hydrocarbon having the following structural formula:

wherein R is selected from thegroup consisting of hydrogen, methyl,.ethyl', propyl, methoxy, ethoxy, chlorine, bromine, fluorine and thecyano radical, is interpolymerized in the proportion of 65% or as aminimum amount to as high as 95% by weight, with a conjugated dioleiinhydrocarbon compound in the proportion of 35% to 5%, working in emulsionform at a temperature ranging from about 25 to 75 C. or higher until themixture of monomers is at least -90% consuitable for being drawn andhatred into shaped articles, wire insulation, solid rods, pressed ormolded articles and for the preparation of coated fabrics of improvedlight resistance, ozone resistance and reduced tackiness. The resinousmaterials formed in accordance with the present invention areparticularly valuable for electrical insulation for high frequencycircuits because of their very low dielectric losses.

In carrying out the process oi this invention a vinyl aromatic compoundof the above formula such as styrene, para methyl-, ethylor propyl'styrene, monoand polychlorinated styrenes, brominated or fluorinatedstyrene, methoxyor ethoxy-styrenes or cyanostyrencs, or the like, isemployed in admixture with a conjugated diene of the type of butadiene,isoprene, piperylene, dimethyl butadiene, chloroprene or other diolefinhaving 4 to 6 carbon atoms capable of polymerization of copolymerizationwith the vinyl aromatic compound in emulsion form. The pre ferred methodis to disperse the reactants in the desired proportions in watercontaining an emulsifying agent such as sodium oleate or other watersoluble soaps or the like and a polymerization catalyst'such aspotassium persulfate or perborate. The mixture Ls then polymerized in apressure vessel for about 10 to 7 hours but preferably for 10 to 24hours at 25 to 75 C. When the reaction is completed or the monomers areat least above 80% converted to polymers, the resulting latex-likedispersion is coagulated by treating the latex with a suitable coagulantsuch as isopropyl alcohol or brine. The coagulate, after washing severaltimes with water and finally with alcohol to remove emulsifiers andsoluble impurities. is dried by any conventional method. It then can beblended with polybutene or other hydrocarbon polymers.

By utilizing the monomers in the ratios disclosed above and by carryingthe conversions to such high levels, i. e. 80% or more, it is possibleto produce products having the necessary physical characteristics, i. e.high molecular weight and high Williams Plasticity-Recovery values.

The effect of high conversions upon the molecular weight of thecopolymer may be readily seen from the following data summarizing theresults obtained by polymerizing styrene and butadiene in a weight ratioof 75 to 25 in aqueous emulsion in accordance with this invention.Samples were withdrawn from the reaction mixture periodically, theconversion determined whereupon the intrinsic viscosity of the productwas determined from which the approximate molecular weight averagevalues were calculated. .The results were as follows:

Percent Molecular Conversion Weight copolymer-s should have an apparentmolecular weight of at least 375,000 to 400,000 and preferably in themolecular weight range of 500,000 to 900,000 inasmuch as the Williamsplasticities of the products in this range are well in excess of 200 at70 C. (5 kg. wt.)

In the event that conversions below about are employed it is necessaryto increase the proportion of styrene or vinyl aromatic compound in thefeed in order to get the desired hardness and molecular weight in theproduct. a

At conversion levels of 80-100%, the polymers which have been crumbwashed and crumb dried are very often insoluble due to the presence ofsubstantial quantities of gel. This naturally would be disadvantageousif it were desired to use the polymer in solution. However, thepreferred method of washing and drying the copolymer produced inaccordance with this invention is by the use of a hot mill (ITO- F.),this treatment having been found to convert any gel present so that acompletely soluble polymer is obtained. In lieu of mill washing anddrying other means of hot mastication such as banburying, extrusion andthe like may be used. Accordingly, it appears that the most desirableproducts are obtained by a combination of high styrene to diene ratios,high conversion with consequent high molecular weight and hotmastication of the copolymer product.

Agents which may be used for emulsifying the monomers in accordance withthe present invention include such substances as alkali metal soaps ofhigher fatty acids such as sodium oleate, sodium salts of selectivelyhydrogenated tallow acids, salts of sulfated amides, salts of sulfatedalcohols, salts of alkyl naphthalene sulfonic acids such as isopropylnaphthalene sulfonic acid, acid type emulsifiers such as the cationactive compounds of high molecular weight amine salts as dodecylaminehydrochloride, Turkey red-oil, and Emulphor type condensation productsof high molecular weight alcohols and ethylene oxide. The amount ofemulsifier is ordinarily about 0.5 to about 5 wt, per cent based on thereactants. For the interpolymerization there is used from about 0.05 toabout 0.6 weight per cent based on the reactants of a polymerizationcatalyst capable of yielding oxygen under the reaction conditions suchas hydrogen peroxide and benzoyl peroxide, and inorganic per salts suchas sodium perborate, sodium persulfate and sodium per carbonate.

The emulsion polymerization reaction may be conducted in the presence ofcatalyst promoters, and modifiers of the type of organic sulfurcompounds such as thio-acids, high molecular weight mercaptans such asbenzyl, or the aliphatic mercaptans having at least 6 carbon atoms permolecule such as octyl, dodecyl, tetradecyl mercaptans and mixtures ofmercaptans such as are obtainable for example from commercial laurylalcohol, nitro hydrazines and amino com pounds. These agents which areused in small amounts, generally 0.05 to 0.25 or 1 or even 2 wt. percent based on the reactants exert a promoting and/or modifying effect onthe reaction and the resulting interpolymers. These materials arereferred to generally hereinafter as polymerization modifiers and arenot to be confused with the polymerization catalysts or oxygen yieldingsubstances described above. The following example is included in orderto illustrate the invention more fully.

EXAMPLE Several runs were carried out in a 3-gallon turbomixer type ofreactor according to the folfor blending with many substances includingoils, waxes, and predominantly hydrocarbon rubberlike polymeric bodies,such as natural rubber, Buna S (butadiene-styrene emulsioninterpolylowing recipe 5 mer), polyethylene, etc. Substances having aStyrene 75 parts further plasticizing action on either of the comIsoprene 25 parts ponent polymers may likewise be added at will LOrOl app r at Start and the usual organic and inorganic fillers or LorolMercaptan 0.05 part at 75% 'Conv. mixtures thereof may be incorporatedtherein. Water 300 parts The interpolymers are useful in combinationSodium soap of selecwith practically any of the natural and synthetictively hydrogenated resins and gums with some of which they form tallowacids (complete true solutions and with others they form adisneutralization) 'lparts perse phase within a continuous phase. TheyPotassium persulfate 0.45 part 5 are particularly useful with suchmaterials as Temperature 50 C. at start the polyindene-coumaron'eresins, the polyvinyl Raised after 50% chlorides, polyvinyl acetylene,polycoumarones,

conversionto 55 C. polyvinyl acetate, polyacrylates and methacry- Raisedafter 75% lates, cellulose esters and ethers, chlorinated rubconversionto 60 C. ber, phenol aldehyde resins, the natural and syn- Conversion93i2% thetic waxes, rosin and natural resins, polya- Time 14-16 hoursmides, factice, alkyd resins, phenol formaldehyde condensation resinssuch as Bakelite, resins obtai n 3 f :o$ :?1?n fi2 i 'ci ;l lgg'g f ifil tfi. mercaptan tained from petroleum residues, hydro rubber, In Spiteof the 3/1 water monomer ratio the mineral waxes, petroleum waxes andvegetable high conversion still yields latices of about 25% fi solidscontent. The latices formed were shorte mtierpolymers alone or mcombination stopped at,the end of the reaction with hydroxwlthpolylsobutylene polythene gutta' ballata, natural or synthetic rubbercan be readily ylamine or hydroquinone, and stabilized with 05-10% of asuitable anti-oxidant such as comPounded with q range of finer mammalsto give new and technically useful compositions. phenyl betanaphthylamine. Th f n t h t ti it m The latex was coagulated by addingthe same 8 0 s represen ve Su e to about an equal. volume of saturatedsodium compoundmg stances chloride brine, below 50 C., whereupon themix- Chlorinated paraifin wax ture was brought to 50 C. and 0.2 N aceticacid Chlorinated olefin polymers added to get the desired particle sizeand then Alkyd resins quenched with 0.2 N NaOH. The slurry was Oxidizedpolymeric materials then diluted with an equal volume of cool waterChlorinated resins and filtered, cake reslurried twice with water Carbonblack, active reinforcing or inactive at 40 c. and then in alkalifollowed by final Clays water washing and drying. Alternatively, theTricresyl phosphate polymer may be mill washed and dried on the Asbestoshot (HO-180 F.) mill. Dibutyl phthalate The results obtained aresummarized in the Wood flour table. Cetyl methacrylate polymer TablePercent Run No. 5253? Initial Temp. O. T211321. T3331? f P632331: 323i Pl a s f l c. Other Data Mercaptan 0. Hours Drying 70 C./5 Kg.

1 0.05 13 95+ 0n mill- 201-59 M. w. 540,000. 2 0.25 so 17 99+ do....10-0 M.w.43e,o00. a 0.05 10 16 98+ do 293-76 M. w. 900,000. 4 {ggiljgggz233E111} 60 93 77 s om e a OOIIV.

1 0.25 mercaptan added: 0.2% initially and 0.05 at conversion.

Norm-In most cases reactor was cleaned prior to each run.

As is apparent from the above examples, this invention is not limited tothe use of any particular emulsifying agent, catalyst, or modfier in thepolymerization reaction, since types other than that disclosed in theexamples may be efl'ectively used.

The olefin-vinyl benzene interpolymers prepared in accordance with thepresent invention are conveniently applicable to many uses, both forblending with polyisobutylene and other olefinic polymers; and also foruse alone for many services such as for protective coatings on metals,wood, fabrics, etc., or for the preparation of self- However, runs #1and 2 were made without intermittent cleaning.

Abalyn (ethyl abietate) Polyesters Polycylopentadiene resins Polymerizedterpenes Polymerized ethylene (polythene) Polyvinyl acetal resin AsphaltPitch Polyhydronaphthalenes Drying oil resins Mineral rubbersHydrogenated terpene polymers Thus the invention presents a new processfor supporting films. They are particularly useful the polymerization ofvinyl aromatic compounds such as styrene with diolefinic materials toyield new and particularly valuable interpolymers, characterized bysubstantial solidity, toughness, flexibility, thermoplasticity and thecapability of compounding with a. wide range of filler substances andother resinous or rubbery substances, to yield a series of particularlyvaluable compositions of matter, particularly suited for the preparationof molded articles in general and electric insulation in particular.

While there are above described a limited number of embodiments of theinvention, it is possible to produce still other embodiments withoutdeparting from the inventive concept herein disclosed and it istherefore desired that only such limitations be imposed on the appendedclaims as are stated therein or required by the prior art.

What we claim and desire to secure by Letters Patent is:

1. In a process for preparing a tough, hard, thermoplastic resin, theimprovement which consists of emulsifying in water a mixture consistingof 75 to 95 wt. per cent of a vinyl aromatic compound corresponding tothe formula CH=CH2 wherein R is selected from the group consisting ofhydrogen, methyl, ethyl, propyl, methoxy, ethoxy, chlorine, bromine,fluorine, and cyano; 25 to wt. per cent of a conjugated diene having 4to 6 carbon atoms per molecule; an emulsifying agent; an oxygen yieldingcatalyst; and 0.05 to 2 wt. per cent based on the weight of the monomerof an aliphatic mercaptan having from 6 to 14 carbon atoms per molecule;and heating the emulsified mixture at a temperature between 25 and 75 C.until at least 80% monomer conversion is reached.

2. In a process for preparing a tough, hard, thermoplastic resin, theimprovement which consists of emulsifying in water a mixture consistingof 75 to 95 wt. per cent of styrene, 25 to 5 wt. per cent of aconjugated diolefin having 4 to 6 carbon atoms per molecule, 0.5 to 5wt. per cent of an emulsifying agent based on monomers, 0.05 to 0.6 wt.per cent of an oxygen yielding catalyst based on monomers, and 0.05 to 1wt. per cent based on monomers of an aliphatic mercaptan having 6 to 14carbon atoms per molecule; and

' heating the emulsified mixture for 10 to 24 hours at a temperaturebetween 25 and C., until at least monomer conversion is reached.

3. A process according to claim 2 wherein the diolefin is butadiene.

4. A process according to claim 2 wherein the diolefln is 2,3-dimethylbutadiene-L3.

5v In a process for preparing a tough, hard, thermoplastic resin, theimprovement which consists of emulsifying in water a mixture consistingof 75 to 95 wt. per cent of styrene, 25 to 5 wt. per cent 01 isoprene,0.5 to 5 wt. per cent of a water soluble soap based on monomers, 0.05 to0.6 wt. per cent of an oxygen yielding catalyst based on monomers, and0.05 to 0.25 wt. per cent based on monomers of an aliphatic mercaptanhaving 6 to 14 carbon atoms per molecule; and heating the emulsifiedmixture for 10 to 24 hours at a temperature between 25 and 75 C. untilat least 80% monomer conversion is reached, whereby a resin having amolecular weight of at least 400,000 is produced.

6. In a process for preparing a tough, hard, thermoplastic resin, theimprovement which consists of emulsifying in water a mixture consistingof 75 wt. per cent of styrene, 25 wt. per cent of isoprene, 0.5 to 5 wt.per cent of sodium oleate based on monomers, 0.05 to 0.6 wt. per cent ofpotassium persulfate based on monomers, and 0.05 to 0.25 wt. per centbased on monomers of an aliphatic mercaptan having predominantly 12carbon atoms per -molecule; and heating the emulsified mixture for 10 to24 hours at a temperature between 25 and 75 C. until at least monomerconversion is reached.

ANTHONY H. GLEASON, PER. K. FROLICH WILLIAM J. SPARKS REFERENCES CITEDThe following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,217,631 Wolfe Oct. 8, 19402,335,124 Konrad et a1. Nov. 23, 1943 2,393,157 Gleason et a1 Jan. 15,1946 FOREIGN PATENTS Number Country Date 456,442 Great Britain Aug. 8,1935

1. IN A PROCESS FOR PREPARING A TOUGH, HARD, THERMOPLASTIC RESIN, THEIMPROVEMENT WHICH CONSISTS OF EMULSIFYING IN WATER A MIXTURE CONSISTINGOF 75 TO 95 WT. PER CENT OF A VINYL AROMATIC COMPOUND CORRESPONDING TOTHE FORMULA